Clinical study visits will take place at the Thai Red Cross AIDS Research Centre, and the optional procedures may occur at the King Chulalongkorn Memorial Hospital. Required laboratory studies that are outlined in this protocol will occur in lieu of those described in the RV 254 protocol. Volunteers may provide separate informed consent for optional procedures to include collection of genital secretions, colon biopsy, inguinal lymph node biopsy, cerebrospinal fluid (CSF) collection via lumbar puncture, and brain Magnetic Resonance Imaging (MRI)/Magnetic Resonance Spectroscopy (MRS)/Diffusion Tensor Imaging (DTI). With separate informed consent, willing participants will undergo archival of peripheral blood mononuclear cells and plasma specimens for research purposes.